Basin Plan Review 2026: Climate Scenarios and Buybacks

The 2026 Basin Plan Review: Climate Scenarios, Water Buybacks and the Search for Honest Planning

Few debates in Australia carry as much emotion as the one over the Murray-Darling Basin. It touches farms and towns, rivers and wetlands, First Nations communities, food prices and the future of rural Australia. And it all comes down to a single question: how much water should be taken out of the rivers, and how much should be left in?

The answer depends partly on a prediction about the future. If the Basin is going to be much drier in coming decades, as some modelling suggests, then the case for recovering more water for the environment looks stronger. If the Basin is not going to dry out that much, the cost to irrigators and communities looks harder to justify.

That’s why a recent analysis by Patrick Byrne, republished on The Daily Declaration from News Weekly, has drawn attention. It argues that the Murray-Darling Basin Authority (MDBA) is relying on a climate scenario that scientists have since scrapped. This post looks at what the review involves, which of the claims stand up, where the picture is more complicated, and how Christians can weigh the competing concerns with care.

What Is the Basin Plan Review?

The Murray-Darling Basin Plan, which came into force in 2012, sets limits on how much water can be taken from the Basin’s rivers for irrigation, towns and industry, so that enough is left for the environment. Under the Water Act 2007, it must be reviewed every ten years to check whether it remains fit for purpose.

The 2026 review has several stages:

• A Basin Plan Evaluation and 2025 Basin Outlook, published in 2025.
• A Sustainable Yields study, published in November 2025, which examined how climate change might affect water availability across the Basin through to 2050.
• A Discussion Paper, released in early 2026, setting out issues and options for consultation. The MDBA says it was intended to test ideas, not to propose final decisions.
• A final Review Report, due to governments in December 2026, to be considered alongside other reviews running in 2026 and 2027.

The review covers many topics, including how water is accounted for, the use of credits, groundwater and how Basin governance works. But the climate question sits at the centre, and it affects how much water recovery, including through buybacks, might be needed.

What the Commentary Argues

Patrick Byrne makes three main claims:

1. The MDBA’s Sustainable Yields report is built on a worst-case climate scenario. The report presents three “storylines” for the Basin: warmer and slightly wetter, warmer and drier, and warmer and much drier. According to Byrne, the MDBA rated the first as only 10 per cent likely and the third as 90 per cent likely, and based the third on the IPCC scenario known as SSP5-8.5.
2. That scenario has been abandoned. In April, around fifty climate scientists who design the scenarios for the IPCC removed SSP5-8.5, saying it had become “implausible.”
3. Historical data tells a different story. Byrne cites Bureau of Meteorology figures showing that, over the past century, the Basin’s maximum temperature has risen by about 1.2°C per century while rainfall has increased by about 6 per cent. He adds that global greening and evaporative cooling moderate warming.

He ends with three questions: why the MDBA relies on modelling that its authors have rejected, why it ignores rising historical rainfall, and where the planning is for new dams.

These are serious questions about public policy that involves billions of dollars and the livelihoods of many communities. They deserve careful checking.

Checking the First Claim: What Did the CMIP7 Paper Say?

The scientific paper Byrne refers to is real. The Scenario Model Intercomparison Project for CMIP7 (ScenarioMIP-CMIP7), led by Detlef van Vuuren and published in Geoscientific Model Development on 7 April 2026, describes the scenario framework for the next round of global climate modelling. It does say that the high-emission levels of the previous round, quantified by SSP5-8.5, “have become implausible,” citing trends in the costs of renewable energy, the emergence of climate policy, and recent emission trends.

But some details matter:

• It’s a design paper by scenario developers, not an IPCC vote. The authors are researchers who help design the scenarios used by climate modellers.
• It didn’t remove the idea of a high-emission future. The new framework includes a “High” scenario, defined as emissions as high as judged plausible, including a rollback of current mitigation policies. The paper says this scenario is expected to give forcing below SSP5-8.5 and describes it as one that “may not be the most likely” but is still plausible.
• The criticism of SSP5-8.5 isn’t new. Researchers such as Zeke Hausfather and Glen Peters argued years ago that the scenario was an unlikely “business as usual” path. The IPCC’s own 2021 report acknowledged that the likelihood of such high-emission scenarios was considered low in light of recent developments.
• The scenario was always meant as a high-end case. Even critics of how the scenario has been used note that it was designed as a very high-end, no-policy possibility, not a forecast.
• There’s a debate about why it became implausible. Some commentators have argued that the scenario was always an extreme case built on very high coal use, rather than a result of recent climate policy.

So the claim that the scenario has been downgraded is broadly supported. The claim that the scientists “scrapped” it and replaced it with something that implies much less warming goes further than the paper says. A lower high-emission scenario still means a warmer world.

Checking the Second Claim: What Does the MDBA Actually Say?

The MDBA’s Sustainable Yields report presents three storylines, which describe possible climate sequences for the 25 years to 2050, such as “hotter and slightly wetter,” “hotter and much drier,” and “hotter and drier with extended drought.” The MDBA states that the storylines are not predictions or forecasts but are examples of what could happen, designed to help people understand what climate change might mean for the Basin. The report also notes that droughts will still occur even in a slightly wetter future.

Byrne says the MDBA assigned 10 and 90 per cent chances to different storylines. I wasn’t able to confirm that in the MDBA’s own summary material, which describes the storylines in terms of percentiles of the modelled climate scenarios rather than as probabilities of what will happen. Readers should check how the percentages are framed in the full report before repeating either characterisation. It’s also worth checking how heavily the review’s conclusions depend on SSP5-8.5 specifically, as opposed to a wider set of modelled scenarios.

This is a legitimate question to put to the MDBA, and the MDBA ought to be able to answer it clearly.

Checking the Third Claim: Has the Basin Been Getting Wetter?

Byrne is right that, over the very long term, rainfall in the Basin as a whole hasn’t fallen. Rainfall averaged across the whole year and across the whole Basin since 1900 shows no steep decline, and wetter periods, including the major La Niña years of 2020 to 2022, have filled storages and brought floods.

But the picture is more complicated:

• Recent decades look different. The Bureau of Meteorology’s State of the Climate reports show a shift towards drier conditions in southern Australia, especially in the cool season from April to October. Since 1994, average April to October rainfall in the south-east has been around 9 per cent lower than in 1900 to 1993.
• Streamflow has fallen more than rainfall. The same reports show that streamflow has decreased at most gauges across southern Australia since 1975. Rivers respond strongly to changes in seasonal rainfall, soil moisture and evaporation.
• The northern Basin. Research from the University of Technology Sydney found that low and no-flow periods in the Darling River since the 1990s were linked to a decrease in late-autumn rainfall, which it attributed to shifts in atmospheric circulation under climate change.
• Higher temperatures increase evaporation. Even where rainfall is steady, warmer conditions mean more water is lost from soils, plants and water surfaces.
• The Millennium Drought from the late 1990s to 2009 and the severe drought of 2017 to 2019 caused enormous hardship, including mass fish kills at Menindee on the Darling in 2018 and 2019.

The evaporative cooling effect described by Bill Priestley, a former CSIRO scientist, in 1966 is real physics: wetter surfaces limit how hot the land surface can get. Global greening has also been documented by NASA satellites, and a 2020 NASA review suggested that it may have reduced global warming by a small amount, in the order of 0.2 to 0.25°C. But these effects moderate warming at the margin. They don’t cancel it, and they don’t change the observed decline in cool-season rainfall and river flows in parts of the Basin.

In short, “the Basin has been getting wetter” is true over a century on average, and a misleading summary of the last few decades.

Buybacks and the People They Affect

Underneath the climate argument is a very human one. Water buybacks, where the government purchases water entitlements from irrigators to return water to the environment, have been controversial for years. Supporters say they’re the most reliable way to recover water. Critics say they remove productive water from farms, reduce irrigated production, raise costs for remaining farmers, and hollow out rural communities.

The Victorian Farmers Federation, for example, has told the review it strongly opposes the Basin Plan’s water recovery targets and further buybacks, arguing that the same environmental outcomes could be achieved through practical works such as improved infrastructure and management, rather than removing water from production. Its submission notes that the MDBA’s own assessment treats extra buybacks as more or less likely in different regions.

On the other side, supporters of water recovery point out that river systems like the Coorong, the Lower Lakes, the Darling and the Basin’s wetlands are under stress, that First Nations communities have cultural connections to rivers and a right to a say, and that over-extraction in earlier decades helped cause the problems the Plan is meant to fix.

Both concerns are legitimate. This is ultimately a question of trade-offs, not a contest between good and bad people.

What About New Dams?

Byrne’s third question is about dams. It’s a fair question, and one that’s been raised for many years. Storage can help smooth supply between wet and dry years, and there’s a strong tradition of dam-building in Australia. There are also trade-offs: suitable sites are limited, big projects are expensive, evaporation losses from shallow storages in hot climates can be high, and dams can change river ecosystems and affect cultural sites. In the Murray-Darling Basin, the larger rivers already have major storages.

The debate over storage deserves a proper cost-benefit analysis rather than slogans on either side.

A Christian Lens

Christians have deep biblical reasons to care about water, land and the people who work it.

Stewardship. Genesis 2:15 describes people placed in the garden to work it and keep it. Psalm 24:1 says the earth is the Lord’s. Caring for rivers, soil and wildlife is part of our calling.

Justice for the farmer and the stranger. Micah 6:8 calls us to act justly and love mercy. Proverbs 31:8–9 tells us to speak up for those who can’t speak for themselves. In the Basin, that includes farming families and small towns that depend on irrigation, and it includes First Nations communities and the river ecosystems themselves.

Honesty. Exodus 20:16 forbids false witness, and Proverbs 11:1 says that dishonest scales are an abomination to the Lord. Presenting evidence accurately, whichever side it favours, is a matter of integrity. Proverbs 18:17 reminds us that the first to state a case seems right until someone comes and examines it.

Prudence in the face of variability. In Genesis 41, Joseph advised Pharaoh to store grain during seven good years to prepare for seven lean years. It’s a biblical picture of planning for drought without knowing exactly when it will come. Proverbs 22:3 says the prudent see danger and take precautions. Luke 14:28 reminds us to count the cost before we build.

Water as a gift. Scripture frequently describes water as a blessing from God (Psalm 65:9–10), and Amos 5:24 calls for justice to roll on like a river. Fair management of a river system is a spiritual concern as well as a technical one.

Our Take

Here’s where we’d like to add some commentary.

1. Good policy needs honest science.

If a government agency relies on a scenario that the scientists who designed it now consider implausible, that’s a fair thing to ask about. The MDBA should explain how its storylines were chosen, what role SSP5-8.5 plays, and how its conclusions would change under other scenarios.

2. But “implausible” isn’t the same as “no problem.”

Retiring a worst-case scenario doesn’t remove the observed drying trend in southern Australia’s cool-season rainfall or the decline in river flows. Planning for a range of futures, including drier ones, is a sensible form of prudence.

3. Be careful with single data points and long-term averages.

A century-long average can hide the recent changes that matter most for farmers and rivers. Equally, a few dry years don’t prove a permanent trend. Both sides should look at multiple measures, including rainfall, runoff, temperature and evaporation.

4. Remember the people.

Behind every buyback figure is a farm, a family, a school, a footy club and a shop on a main street. Behind every environmental flow is a river, a wetland and sometimes a community with a cultural connection that stretches back thousands of years. Policy that forgets either will fail.

5. Look for solutions that serve both.

Where possible, Christians can advocate for approaches that serve people and rivers together, such as infrastructure upgrades, efficient irrigation, targeted environmental works, better monitoring, community input and transparent evidence.

6. Hold your confidence loosely.

Climate and hydrology are complex, and projections carry real uncertainty in both directions. We can recognise that uncertainty without falling into either panic or dismissal.

The Other Side of the Argument

In fairness, here is how those with different views might respond:

• The MDBA and climate scientists would say that the storylines are intended to explore plausible risks, not to forecast, that planning for the dry end of the range is prudent given observed trends, and that the Basin Plan has long been criticised for not taking climate change seriously enough.
• Environmental groups would argue that the rivers have already been over-allocated, that recovering water is essential for ecological health and cultural values, and that delaying action risks irreversible damage.
• First Nations voices would emphasise that Aboriginal communities have long been excluded from water planning and that cultural flows are a matter of justice.
• Irrigators and regional communities would argue that buybacks have damaged their livelihoods, that the climate modelling has been used to justify further cuts, and that practical works should come first.
• Climate scientists might also note that the lower high-emission scenario still produces a warmer Basin, and that analysts such as Roger Pielke Jr. have argued the old extreme scenario was always unrealistic and was not made implausible by climate policy.

A fair reader can take the strongest points from each.

How to Engage

• Read the primary documents. The MDBA’s Discussion Paper, the Sustainable Yields report and the CMIP7 paper are all public. Check what they actually say.
• Follow the timeline. The Review Report goes to governments in December 2026, so there’s still time to contact your MP, local council, irrigation group or community organisation.
• Support local voices, including rural churches and community groups who are supporting families under pressure.
• Look at the whole picture. Read perspectives from farmers, scientists, environmental groups and First Nations leaders.
• Pray for wise decisions, for rural communities, and for rains in due season.

Questions to Reflect On

• Have I formed a view of the Basin debate from a single source?
• What would it take for me to change my mind?
• How do I weigh the needs of farming communities, rivers and First Nations cultural values?
• What would good stewardship of a shared river system look like in practice?
• How could my church support a rural community under pressure?

A Short Prayer

Lord, you give the rain and fill the rivers. We thank you for the land and the water that sustain so many lives. Give wisdom to those who make decisions about the Basin, honesty to those who present the evidence, and fairness to those who weigh competing needs. Sustain farming families and rural towns, protect the rivers and wetlands, and honour the cultural connections of First Nations peoples. Teach us to plan with prudence, to speak with integrity, and to care for what you have entrusted to us. Amen.